NP6.2 | Turbulence, magnetic reconnection, shocks and particle acceleration: nonlinear processes in space, laboratory and astrophysical plasmas
EDI
Turbulence, magnetic reconnection, shocks and particle acceleration: nonlinear processes in space, laboratory and astrophysical plasmas
Co-organized by ST1
Convener: Maria Elena Innocenti | Co-conveners: Francesco Pucci, Rungployphan KieokaewECSECS, Giovanni Lapenta
Orals
| Thu, 27 Apr, 08:30–10:15 (CEST)
 
Room 0.16
Posters on site
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
Hall X5
Posters virtual
| Attendance Thu, 27 Apr, 16:15–18:00 (CEST)
 
vHall ESSI/GI/NP
Orals |
Thu, 08:30
Thu, 16:15
Thu, 16:15
Space, laboratory, and astrophysical plasmas are seemingly different environments, which however host very similar processes: among them, turbulence, magnetic reconnection, kinetic instabilities and shocks, which all result in particle acceleration and plasma heating. These processes are highly non-linear, and closely interlinked. On one hand, the turbulence cascade favors the onset of magnetic reconnection between magnetic islands and, on the other hand, magnetic reconnection can trigger turbulence in the reconnection outflows and separatrices. Similarly, shocks may form in collisional and collisionless reconnection processes and can be responsible for turbulence generation, as for instance in the turbulent magnetosheath.
The investigation of these processes based on simulations and observations are converging. Simulations can deliver output that is approaching, in temporal and spatial scales and in the coexistence of several scales, the complexity of an increasing number of the processes of interest. On the observation side, high cadence measurements of particles and fields, high resolution 3D measurements of particle distribution functions and multipoint measurements make it easier to reconstruct the 3D space surrounding the spacecraft. The ever growing amount of data that both simulations and observations produce can be then combined through and exploited with Artificial Intelligence and Machine Learning methods.
This session welcomes numerical, observational, and theoretical works relevant for the study of the above mentioned plasma processes. Particularly welcome this year will be works focusing on the common aspects of turbulence, reconnection, and shocks in space, laboratory, and astrophysical plasmas.

Orals: Thu, 27 Apr | Room 0.16

08:30–08:35
Magnetic reconnection
08:35–08:45
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EGU23-11279
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On-site presentation
Binbin Tang, Hanwen Wang, Wenya Li, Yongcun Zhang, Daniel Graham, Yuri Khotyaintsev, Chunhui Gao, Xiaocheng Guo, and Chi Wang

Magnetic reconnection is a fundamental process that rapidly converts energy from the magnetic field to plasma. Recent studies have shown that a large parallel electric field (E) can appear in guide-field reconnection, and its magnitude can be several times larger than the reconnection electric field. However, the generation of this large E is still not fully understood, and the reaction of electrons to this E has not been fully investigated. In this study, we focus on these issues in a strong guide-field reconnection event (the normalized guide field is ~ 1.5) from Magnetospheric Multiscale (MMS) observations. With the presence of a large E in the electron current sheet, electrons are accelerated when streaming into this E region from one direction, and decelerated from the other direction. Some decelerated electrons can reduce the parallel speed to ~ 0 to form relatively isotropic electron distributions at one side of the electron current sheet, as the estimated acceleration potential (Φ ~ 2 kV) satisfies the relation eΦ ≥ kT, where T is the electron temperature parallel to the magnetic field. Therefore, a large E is generated to balance the parallel electron pressure gradient across the electron current sheet, since electrons at the other side of the current sheet are still anisotropic. Based on these observations, we further show that the electron beta is an important parameter in guide-field reconnection, providing a new perspective to solve the large parallel electric field puzzle in guide-field reconnection.

How to cite: Tang, B., Wang, H., Li, W., Zhang, Y., Graham, D., Khotyaintsev, Y., Gao, C., Guo, X., and Wang, C.: Electron dynamics in guide-field magnetic reconnection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11279, https://doi.org/10.5194/egusphere-egu23-11279, 2023.

08:45–08:55
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EGU23-6702
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ECS
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Highlight
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On-site presentation
Kevin Alexander Blasl, Takuma Nakamura, Rumi Nakamura, Adriana Settino, Zoltan Vörös, Martin Hosner, Daniel Schmid, Martin Volwerk, Owen Wyn Roberts, Evgeny Panov, Yi-Hsin Liu, Ferdinand Plaschke, Hiroshi Hasegawa, Julia Stawarz, and Justin Craig Holmes

The Kelvin-Helmholtz instability (KHI) excited at the Earth’s magnetopause has been considered responsible for causing efficient mass and energy transfer across the magnetopause. Theoretical, numerical and observational studies have revealed that the evolution of the KHI and the resulting nonlinear vortex flow involve secondary processes. As a unique case of such multi-scale and inter-process couplings, we recently reported observations of the MHD-scale KH waves and embedded smaller-scale phenomena in data from NASA’s Magnetospheric Multiscale (MMS) mission at the dusk- flank magnetopause during southward interplanetary magnetic field (IMF) conditions. Given quantitative consistencies with corresponding fully-kinetic particle-in-cell (PIC) simulations designed for this event, the MMS observations demonstrate the onset of the Lower-Hybrid Drift Instability (LHDI) during the nonlinear phase of the KHI and the subsequent turbulence and mixing of plasmas near the boundary layer.

In this study, we further explored this southward IMF KHI event and found signatures of magnetic reconnection in an electron-scale current sheet observed in the KH vortex-driven LHDI turbulence. This reconnection event was observed under high guide field conditions and features a super-Alfvénic electron outflow, a Hall perturbation of the magnetic field and enhanced energy conversion. Results from a high-resolution PIC simulation designed for this reconnecting current sheet suggest a highly dynamical current sheet evolution, quantitatively consistent with the observations made by MMS.

In addition, results from statistical studies utilizing data from several KH wave/vortex edge crossings throughout this southward IMF KH event show that the formation of electron-scale current sheets due to the interplay of the KHI and LHDI would be a ubiquitous phenomenon at least under the observed conditions of this magnetopause event and thus an important factor in the study of cross-scale energy transfer of the KHI.

How to cite: Blasl, K. A., Nakamura, T., Nakamura, R., Settino, A., Vörös, Z., Hosner, M., Schmid, D., Volwerk, M., Roberts, O. W., Panov, E., Liu, Y.-H., Plaschke, F., Hasegawa, H., Stawarz, J., and Holmes, J. C.: Electron-scale reconnecting current sheet formed within the lower hybrid wave-active region of Kelvin-Helmholtz waves, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6702, https://doi.org/10.5194/egusphere-egu23-6702, 2023.

08:55–09:05
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EGU23-5905
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ECS
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On-site presentation
Saba Khalid and Muhammad Nouman Sarwar Qureshi

Magnetic reconnection interlinks different regions of plasmas by converting magnetic energy into plasma heating and energization of particles. It causes abrupt changes in the temperature, density, field strength and flow speed. The physical mechanism behind charge particle energization during magnetic reconnection is best explained by the concept of double layers (DLs) and associated parallel electric fields. In-situ observations of reconnection sites by Magnetospheric Multi Scale (MMS), THEMIS and FAST have confirmed that charge particle energization in these regions is associated with large parallel electric fields in auroral regions, Earth’s plasma sheet and separatrix region of Earth’s magnetosphere. The reported literature motivated us to investigate double layers and associated electric field at the reported sites by using multi-fluid theory for electron-ion plasma and employing fully nonlinear Sagdeev potential approach. We have considered the ion inertial effect whereas electrons are assumed to be non-Maxwellian following (r, q) distribution function. In particular, parallel electric fields associated with Alfvenic double layer have been investigated at non-Maxwellian effective temperature scales and then compared with the observations. We have seen that the characteristics of DLs associated with the kinetic Alfvén waves are significantly modified due to the nonthermal parameters r and q, propagation angle 𝜃, and Alfvénic Mach number 𝑀A. Our current study supports both the compressive and rarefactive double layer structures.

How to cite: Khalid, S. and Qureshi, M. N. S.: Parallel Electric Field and Double Layers at Non-Maxwellian Effective Temperature Scales in Near Earth Space Plasmas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5905, https://doi.org/10.5194/egusphere-egu23-5905, 2023.

09:05–09:15
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EGU23-10735
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On-site presentation
Huijie Liu, Wenya Li, Binbin Tang, Cecilia Norgren, Daniel Graham, Yuri Khotyaintsev, Daniel Gershman, James Burch, and Chi Wang

High-speed electron flows play an important role in the energy dissipation and conversion in the terrestrial magnetosphere and are widely observed in regions related to magnetic reconnection, e.g., the vicinity of electron diffusion regions (EDRs), and separatrix layers. NASA’s Magnetospheric Multiscale mission was designed to resolve the electron-scale kinetic processes of Earth’s magnetosphere. Here, we perform a systematic survey of high-speed electron flows in the terrestrial magnetotail using the MMS observations from 2017 to 2021. The high-speed electron flows are characterized by electron bulk speeds larger than 5000 km/s. We identified 649 events. Those events demonstrate unambiguous dawn-dusk asymmetry, and 73% of them locate in the dusk magnetotail. The selected events are found in EDRs, the reconnection separatrix boundary layer, and the lobe region. More than 70% of the events are identified in the separatrix boundary layer and the lobe region and are aligned with the ambient magnetic field. 75 cases, with magnetic field magnitude smaller than 5 nT, locate near the plasma-sheet neutral line. Approximately 20 cases among them have EDR signatures, and those high-speed electron flows are directed arbitrarily with respect to the ambient magnetic field. We also show other statistical properties of the events, including electron bulk speed, electron number density, and temperature anisotropy. 

How to cite: Liu, H., Li, W., Tang, B., Norgren, C., Graham, D., Khotyaintsev, Y., Gershman, D., Burch, J., and Wang, C.: Statistics of the high-speed electron flows in the magnetotail, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10735, https://doi.org/10.5194/egusphere-egu23-10735, 2023.

Turbulence and instabilities
09:15–09:25
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EGU23-3017
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ECS
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Highlight
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On-site presentation
Xinmin Li, Rongsheng Wang, Can Huang, Quanming Lu, and San Lu

A long-outstanding issue in fundamental plasma physics is how magnetic energy is finally dissipated in kinetic scale in the turbulent plasma. Based on the Magnetospheric Multiscale mission data in the plasma turbulence driven by magnetotail reconnection, we establish the quantitative relation between energy conversion (J·E , J is current density and E is electric field) and current density (J). The results show that the magnetic energy is primarily released in the perpendicular directions (up to 90%), in the region with current density less than 2.3 Jrms, where Jrms  is the root mean square value of the total current density J. In the relatively weak current region (< 1.0 Jrms ), the ions get most of the released energy while the largely negative energy conversion rate of the electrons means a dynamo action. In the strong currents (>1.0 Jrms), the ion energization was negligible and the electrons are significantly energized. Moreover, a linearly increasing relationship was established between J·E and J. The observations indicate that ions overall dominate energy conversion in turbulence, but the electron dynamics are crucial for energy conversion in intense currents and the turbulence evolution.

How to cite: Li, X., Wang, R., Huang, C., Lu, Q., and Lu, S.: Energy Conversion and Partition in Plasma Turbulence Driven by Magnetotail Reconnection, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3017, https://doi.org/10.5194/egusphere-egu23-3017, 2023.

09:25–09:35
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EGU23-6253
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Highlight
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On-site presentation
Zoltan Vörös, Owen Wyn Roberts, Luca Sorriso-Valvo, Emiliya Yordanova, Yasuhito Narita, Rumi Nakamura, and Ferdinand Plaschke

The terrestrial magnetosheath (MS) represents a turbulent, high-beta, compressional, sporadically Alfvenic environment which contains the shocked solar wind (SW) magnetized plasma permeated with waves, instabilities and structures of various origins. In the processes of interaction of the structured SW with the shock and the MS, the electromagnetic, kinetic and thermal energies are transported between locations,  transferred between scales, conversed between each other and finally dissipated. Similarly to the SW case the energy transfer in MS is expected to be manifested in typical scalings seen in power spectral densities of various field and plasma parameters  over the fluid (inertial-range) and kinetic ion-electron scales. However, near the sub-solar dayside MS the inertial-range turbulent cascade is usually absent, while the kinetic range scaling roughly remains the same as in the SW. Observations of short magnetic correlation lengths near the sub-solar MS also confirm the absence of large-scale magnetic fluctuations which could populate the inertial-range of scales. Without the inertial range energy cascade the kinetic range turbulence should exhibit a fast decay downstream of the shock, but it is not observed. We argue that to understand the spectral scalings in the MS the whole energy budget has to be considered including possible nonlocal energy transfer terms. By using MMS data in the MS we show that, when the inertial range is present, the turbulent energy dissipation rate can be estimated by the energy transfer rate from both the Yaglom law and from the pressure-strain interaction term. When the inertial range is absent and the Yaglom law cannot be used,  the dissipation rate can still be estimated by using the pressure-strain term.

How to cite: Vörös, Z., Roberts, O. W., Sorriso-Valvo, L., Yordanova, E., Narita, Y., Nakamura, R., and Plaschke, F.: Turbulent energy transfer and dissipation in the terrestrial magnetosheath, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6253, https://doi.org/10.5194/egusphere-egu23-6253, 2023.

09:35–09:45
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EGU23-12262
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ECS
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solicited
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On-site presentation
Adriana Settino, Rumi Nakamura, Kevin A. Blasl, Takuma Nakamura, Denise Perrone, Francesco Valentini, Owen Wyn Roberts, Evgeny Panov, Zoltan Vörös, Martin Volwerk, Daniel Schmid, Martin Hosner, Daniel B. Graham, and Yuri V. Khotyaintsev

The Kelvin-Helmholtz (KH) instability is a shear-driven instability commonly observed at the Earth’s magnetopause under different solar wind conditions. The evolution of the KH instability is characterised by the nonlinear coupling of different modes, which tend to generate smaller and smaller vortices along the shear layer. Such a process leads to the conversion of energy due to the large-scale motion of the shear flow into heat contributing to the local heating and the generation of a turbulent environment. On the other hand, it allows the entry of the dense and cold solar wind plasma into the tenuous and hot magnetosphere, thus favoring the mixing of these two different regions.

In this context, we introduce a new quantity, the so-called mixing parameter, which can identify the vortex boundaries and distinguish among different types of KH structures crossed by the spacecraft. The mixing parameter exploits the well distinct particle energies which characterise the magnetosphere and magnetosheath plasmas by using only single-spacecraft measurements [1]. The mixing parameter is therefore used to conduct a statistical analysis of the evolution of KH structures observed by the Magnetospheric Multiscale mission in the near Earth’s environment for two specific interplanetary magnetic field configurations: northward and southward. Moreover, in situ measurements are compared with kinetic KH instability simulations modeling realistic conditions observed by the satellites. The good agreement between synthetic data and in situ observations further strengthen our interpretation of the mixing parameter features and results.

 

[1] Settino, A., et al. (2022) Journal of Geophysical Research: Space Physics, 127, e2021JA029758.

How to cite: Settino, A., Nakamura, R., Blasl, K. A., Nakamura, T., Perrone, D., Valentini, F., Roberts, O. W., Panov, E., Vörös, Z., Volwerk, M., Schmid, D., Hosner, M., Graham, D. B., and Khotyaintsev, Y. V.: Plasma mixing during active Kelvin-Helmholtz instability at the Earth’s magnetopause under different interplanetary magnetic field configurations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12262, https://doi.org/10.5194/egusphere-egu23-12262, 2023.

09:45–09:55
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EGU23-15616
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On-site presentation
Luca Franci, Emanuele Papini, Daniele Del Sarto, Alfredo Micera, Julia Stawarz, Tim Horbury, Giovanni Lapenta, Harry Lewis, Chadi Salem, Simone Landi, Petr Hellinger, Lorenzo Matteini, Antonio Cicone, Mirko Piersanti, Maria Elena Innocenti, Milan Maksimovic, and David Burgess

We model plasma turbulence in the near-Sun solar wind by means of a high-resolution fully kinetic simulation initialised with average plasma conditions measured by Parker Solar Probe during its first solar encounter. Once turbulence is fully developed, the power spectra of the plasma and electromagnetic fluctuations exhibit clear power-law intervals down to sub-electron scales. Our simulation models the electron-scale electric field fluctuations with unprecedented accuracy. This allows us to perform the first detailed analysis of the different terms of the electric field in the generalised Ohm's law (MHD, Hall, and electron pressure terms) at ion and electron scales, both in physical space and in Fourier space. Such analysis suggests rewriting the Ohm’s law in a different form, which disentangles the contribution of different underlying plasma mechanisms, characterising the nature of the electric field fluctuations in the different range of scales. This provides a new insight on how energy in the turbulent electromagnetic fields is transferred through ion and electron scales and seems to favour the role of pressure-balanced structures versus waves. We finally test our assumptions and numerical results by means of a statistical analysis using magnetic field, electric field, and electron density data from Solar Orbiter and Parker Solar Probe. Preliminary results show good agreement with our theoretical expectations inspired by our simulation.

How to cite: Franci, L., Papini, E., Del Sarto, D., Micera, A., Stawarz, J., Horbury, T., Lapenta, G., Lewis, H., Salem, C., Landi, S., Hellinger, P., Matteini, L., Cicone, A., Piersanti, M., Innocenti, M. E., Maksimovic, M., and Burgess, D.: On the nature of electric field fluctuations in the near-Sun solar wind and its implication for the turbulent energy transfer at ion and electron scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15616, https://doi.org/10.5194/egusphere-egu23-15616, 2023.

09:55–10:05
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EGU23-16725
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On-site presentation
Leon Ofman, Lynn B Wilson, Teresa Nieves-Chinchilla, Lan Jian, and Adam Szabo

Heliospheric shocks associated with interplanetary coronal mass ejections (ICMEs) were observed by Wind, and DSCOVR at L1, STEREO spacecraft at ~1AU, and recently by the Parker Solar Probe in the inner heliosphere. The magnetic structure and the downstream magnetic oscillations were detected by Wind with 10.9 samples/s and DSCOVR with 50 samples/s. However, the velocity distributions of the protons are available at much lower cadence, and the potentially important interaction between  the alpha particles and  the heliospheric shocks are difficult to obtain directly from present data. Since the alpha particles in the solar wind are the second most abundant ion that can carry significant energy, momentum and mass flux of the solar wind, the alphas can significantly affect the propagation of these shocks. Recently, using hybrid-(PIC) models we studied the effects of alpha particles on the structure and magnetic oscillations of oblique high Mach number heliospheric shocks, and found that the magnetic and density structures of these shocks are significantly affected by the alpha particles with typical solar wind relative abundances. Here, we extend the study and report the results of new hybrid models of oblique shocks guided by observations. We investigate the typical observed relative solar wind abundances of alphas, Mach numbers, and shock normal directions, and compare the results for the various shock parameters. We model the effects of alpha particles properties on the shock ramp, wake, and downstream oscillations and study the properties of proton and alpha particle velocity distribution functions (VDFs) and the kinetic waves downstream of the shocks in the inner heliosphere. We expand the model and study for the first time the effects of relative streaming of proton-alpha ion populations as well as the ion anisotropies on the shock propagation. We investigate the effects of the ion kinetic properties on the heliospheric shock structures and discuss how the modeling results can improve the interpretation of spacecraft observations of these shocks. 

How to cite: Ofman, L., Wilson, L. B., Nieves-Chinchilla, T., Jian, L., and Szabo, A.: Investigating the interactions of alpha particles in collisionless oblique heliospheric shocks, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16725, https://doi.org/10.5194/egusphere-egu23-16725, 2023.

10:05–10:15
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EGU23-3604
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ECS
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On-site presentation
Daniela Maci, Rony Keppens, and Fabio Bacchini

Turbulent states of motion are almost unavoidable in fluids, gases, and plasmas. The ubiquitous presence of turbulence largely contributes to the central role that its study holds in many research fields. This work focuses on space and astrophysical plasmas, where magnetohydrodynamic turbulence is observed nearly everywhere. However, it builds on an issue that is shared by all turbulence-related field of studies: direct numerical simulations (DNS), required to verify turbulent states properties such as scaling law behaviors, require substantial computing resources.

The presentation will introduce the audience to BxC[1], an analytic generator of realistic-looking turbulent magnetic fields, that computes 3D O(10003 grid points) solenoidal vector fields in minutes to hours on desktops. The model is inspired by recent developments in 3D incompressible fluid turbulence theory: intermittent, multifractal random fields are generated through non-linear transformations of a Gaussian white noise vector, combined to specifically designed geometrical constructions. Furthermore, the model is implemented starting from a modified Biot-Savart law, which allows for a clear interpretation of the BxC parameters.

The turbulent magnetic field realized with BxC is then compared and validated against a much more computationally expensive DNS in terms of: (i) characteristic sheet-like structures of current density, (ii) volume-filling aspects across current intensity, (iii) power-spectral behaviour, (iv) probability distribution functions of increments for magnetic field and current density, structure functions, spectra of exponents, and (v) partial variance of increments.

 

[1] Durrive, J.-B., Changmai, M., Keppens, R., Lesaffre, P., Maci, D., and Momferatos, G. (2022). Swift generator for three-dimensional magnetohydrodynamic turbulence. Phys. Rev. E, 106:025307

How to cite: Maci, D., Keppens, R., and Bacchini, F.: Swift generator for 3D magnetohydrodynamic turbulence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3604, https://doi.org/10.5194/egusphere-egu23-3604, 2023.

Posters on site: Thu, 27 Apr, 16:15–18:00 | Hall X5

Magnetic reconnection
X5.350
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EGU23-11615
Wenya Li, Binbin Tang, and Chi Wang

Magnetic reconnection is a fundamental process in collisionless space plasma, and the electron-scale kinetic physics at the X line controls how the magnetic field lines break and reconnect. The four spacecraft of the Magnetospheric Multiscale (MMS) mission encountered an X line of symmetric reconnection in the terrestrial magnetotail on 27 August 2018. Here, we present the electron-scale dynamics and the generalized Ohm’s law (GOL) analysis of this case. Its two-dimensional structure, magnetic topology, and electron streamline map are reconstructed based on a time-independent and inertialess form of electron magnetohydrodynamic (eMHD) equation. We map the electron velocity distribution functions (VDFs) along the MMS trajectories through the X line, covering the two-side inflow and reconnected regions, and the typical electron motions for forming the observed VDFs are also presented. The observed reconnection electric field EM is approximately 2-3 mV/m and predominantly balanced by the spatial gradient of the electron pressure off-diagonal term PeMN, which is mostly contributed by the electron meandering motion at the X line. Our results show the electron-scale dynamics and the associated electron VDFs at an X line and their role in the electron force balance.

How to cite: Li, W., Tang, B., and Wang, C.: Electron-scale dynamics and generalized Ohm’s law of an MMS X-line encounter on 27 August 2018, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11615, https://doi.org/10.5194/egusphere-egu23-11615, 2023.

X5.351
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EGU23-5887
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ECS
Louis Richard, Yuri V. Khotyaintsev, Daniel B. Graham, Andris Vaivads, Daniel J. Gershman, and Christopher T. Russell

Magnetotail magnetic reconnection results in fast plasma flows referred to as jets. Reconnection jets are populated with complex non-Maxwellian ion distributions providing a source of free energy for the micro-instabilities, which contribute to the ion heating in the reconnection region. We present a statistical analysis of the ion temperature anisotropy in magnetic reconnection jets using data from the Magnetospheric Multiscale spacecraft. Compared with the quiet plasma in which the jet propagates, we often find anisotropic and non-Maxwellian ion distributions in the plasma jets. We observe magnetic field fluctuations associated with unstable ion distributions, but the wave amplitude is not large enough to scatter ions during the observed lifetime of the jet. Our estimate of the phase-space diffusion due to chaotic and quasi-adiabatic ion motion in the current sheet shows that the diffusion is sufficiently fast to be the main process leading to isotropization.

How to cite: Richard, L., Khotyaintsev, Y. V., Graham, D. B., Vaivads, A., Gershman, D. J., and Russell, C. T.: Ion Temperature Anisotropy in Plasma Jets, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5887, https://doi.org/10.5194/egusphere-egu23-5887, 2023.

X5.352
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EGU23-17214
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Highlight
Matti Ala-Lahti, Tuija Pulkkinen, Julia Ruohotie, Mojtaba Akhavan-Tafti, Simon Good, and Emilia Kilpua

In the solar wind, a bifurcated current sheet is often observed in a reconnection outflow region as predicted by the original Petchek reconnection model, with the detailed exhaust structure becoming more complex when asymmetries between reconnecting plasmas are present. Here we present the first multi-spacecraft mission in-situ observations of a solar wind reconnection exhaust populated with filamentary (Hall) currents at an interplanetary coronal mass ejection (ICME) sheath—ejecta boundary. At the ICME sheath—ejecta boundary, asymmetric inflow conditions control reconnection, a relatively hot and dense plasma of the sheath coupling with the sparse low-beta ejecta plasma. These novel high-resolution observations demonstrate a multi- layered exhaust, and speak for the opportunities that future missions, such as HelioSwarm, and Parker Solar Probe and Solar Orbiter open for investigating magnetic reconnection in the solar wind.

How to cite: Ala-Lahti, M., Pulkkinen, T., Ruohotie, J., Akhavan-Tafti, M., Good, S., and Kilpua, E.: Magnetic reconnection in the solar wind: Filamentary currents in a multi-layered exhaust region at an ICME sheath—ejecta boundary, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17214, https://doi.org/10.5194/egusphere-egu23-17214, 2023.

X5.353
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EGU23-11637
Maria Elena Innocenti, Fulvia Pucci, Elisabetta Boella, Anna Tenerani, and Jeremy Dargent

In this study, we use fully kinetic Particle In Cell (PIC) simulations to investigate numerically the dispersion relation of the tearing instability in the kinetic regime, which is at the moment rather poorly explored by theoretical investigations. To reduce the computational cost of the simulations, we use the the semi-implicit, energy conserving ECsim code (Lapenta et al, 2017), that allows us to step over the smaller scales and fastest frequencies and focus on characteristic scales of interest, with excellent energy conservation.

We run several simulations with current sheets of fixed length. The current sheet half-thickness is progressively increased from $\delta \sim d_i$ to significantly larger. The other simulation parameters are kept identical.

In our simulations, the tearing instability grows without external perturbation from the particle noise of PIC simulations. Later onset times are (predictably) observed when the number of particles per cell is increased.

Several modes grow unstable in each simulation. We plot the growth rates of the unstable modes as a function of the current sheet thickness. We obtain a spread around a curve decreasing with increasing current sheet thickness. 

How to cite: Innocenti, M. E., Pucci, F., Boella, E., Tenerani, A., and Dargent, J.: A numerical study of tearing instability growth rate as a function of current sheet thickness in the kinetic regime, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11637, https://doi.org/10.5194/egusphere-egu23-11637, 2023.

X5.354
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EGU23-15797
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Highlight
Patricio A. Munoz, Xiaowei Zhou, and Jörg Büchner

Current sheets are the fundamental structures that store magnetic energy in astrophysical plasmas, such as planetary magnetospheres and solar flares. This free energy can then be explosively released by magnetic reconnection. This process has been traditionally modeled by highly idealized models such as the so-called Harris current sheet equilibrium. But recently, a new class of current sheet equilibrium has been analytically  developed, which takes into account several features of recently observed current sheets in planetary magnetotails. Those features include an embedded multi-layer structure, electron temperature anisotropy and a non-linear magnetic field profile in the (inner) electron inner layer which also includes a normal magnetic field component.
Here we present the analysis of the so-far unknown stability properties of this new current sheet equilibrium by means of fully kinetic Particle-in-Cell (PIC) numerical simulations. We used parameters appropriate for the current sheets in diverse planetary magnetotails.
Our results allow us to make more realistic predictions concerning the development of magnetic reconnection in those magnetotails compared to the standard Harris current sheet models.

How to cite: Munoz, P. A., Zhou, X., and Büchner, J.: Stability properties of a new anisotropic current sheet equilibrium for planetary magnetotails, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15797, https://doi.org/10.5194/egusphere-egu23-15797, 2023.

X5.355
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EGU23-8086
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ECS
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Highlight
Jeremy Dargent, Sergio Toledo-Redondo, Andrey Divin, and Maria Elena Innoncenti

This work investigates the energy transfer in the process of collisionless antiparallel magnetic reconnection and its dependance to the velocity distribution function of the inflowing plasma. We realised two two-dimensional semi-implicit PIC simulations of symmetric reconnection with exactly the same global parameters, but with different distributions of plasma: one simulation is loaded using Maxwellian distributions, while the other is the sum of two Maxwellian distributions, a hot one and a cold one, resulting in a very peaked distribution with large tails. We measure the increase of the bulk and thermal kinetic energies in both simulation for each population and compare it to the loss of magnetic energy through a contour surrounding the ion diffusion region. We show that the global energy budget for ions and electrons does not change depending on the distribution function of the plasma, but also that, when focusing on sub-populations, the hot ion population (i.e. the tail of the distribution) get more thermal energy than the cold ion population (i.e. the core of the distribution).

How to cite: Dargent, J., Toledo-Redondo, S., Divin, A., and Innoncenti, M. E.: Energy conversion by magnetic reconnection in multiple ion temperature plasmas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8086, https://doi.org/10.5194/egusphere-egu23-8086, 2023.

Turbulence
X5.356
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EGU23-14458
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ECS
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Jeremiah Lübke, Frederic Effenberger, Horst Fichtner, and Rainer Grauer

The transport of cosmic rays in turbulent magnetic fields is commonly investigated by solving the Newton-Lorentz equation of test particles in synthetic turbulence fields. These fields are typically generated from superpositions of Fourier modes with prescribed power spectrum and uncorrelated random phases, bringing the advantage of covering a wide range of turbulence scales at manageable computational effort. However, almost all of these models to date only account for second-order Gaussian statistics and thus fail to include intermittent features. Recent observations of the solar wind suggest that astrophysical magnetic fields are strongly non-Gaussian, and the question of how such higher-order statistics impact cosmic ray transport has only received limited attention. To address this, we present an algorithm for generating synthetic turbulence based on Kolmogorov’s log-normal model of intermittency. It generates a divergence-free magnetic field by computing the curl of a vector potential, which in turn is obtained from an inverse wavelet transform of a continuous log-normal cascade process. We investigate the statistics of the generated fields, show that anomalous scaling properties are accurately reproduced and discuss implications on cosmic ray transport. *Supported by DFG (SFB 1491)

How to cite: Lübke, J., Effenberger, F., Fichtner, H., and Grauer, R.: Modelling magnetic turbulence with log-normal intermittency by continuous cascades, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14458, https://doi.org/10.5194/egusphere-egu23-14458, 2023.

X5.357
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EGU23-13090
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ECS
Otman Ben Mahjoub and Aziz Ouadoud

The present research aims to study the influence of multiscale fractal geometry on the generation and decay of turbulence by spaced fractal square grid (SFSG) in order to understand how the turbulent flow is modified when it is generated at different scales. Velocity measurements were made in an open-circuit suction wind tunnel at various positions downstream of the grid in the streamwise and spanwise direction for three different inlet velocities using a constant temperature hot wire anemometer. The SFSG pattern producing a multiscale forcing of velocity is new and is the one used as the basis for this project. It was found that this space-filling grid model with relatively low solidity has the ability to generate turbulence with high turbulence intensity and high Reynolds numbers compared to the turbulence generated by fractal square grid (FSG) and regular grids at the same flow velocity. A more comprehensive understanding of this type of multiple length scales in momentum and energy transport has a key role to understand the analysis of structural implications due to the pollutant dispersion in the atmosphere.

How to cite: Ben Mahjoub, O. and Ouadoud, A.: The influence of multiscale fractal geometry on the generation of turbulence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13090, https://doi.org/10.5194/egusphere-egu23-13090, 2023.

Posters virtual: Thu, 27 Apr, 16:15–18:00 | vHall ESSI/GI/NP

Magnetic reconnection
vEGN.3
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EGU23-6224
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ECS
The Effect of Ion Gyroradius in the Transition from Electron-only to Ion-coupled Reconnection
(withdrawn)
Yundan Guan
vEGN.4
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EGU23-9773
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Kittipat Malakit, Theerasarn Pianpanit, Pakkapawn Prapan, David Ruffolo, Peera Pongkitiwanichakul, Michael Shay, Paul Cassak, and Piyawat Suetrong

During 2D magnetic reconnection, plasma is normally understood to flow from one of the inflow sides into the diffusion region and then turn sharply and join the outflow on the same side. Using particle-in-cell simulations with a modification to allow us to label ions and electrons by their initial locations, we find that inflowing plasma does not join the outflow on the same side; instead, plasma crosses to the other inflow side before changing direction to produce an outflow jet. Furthermore, we find that ions and electrons undergo different crossover mechanisms leading to different crossing patterns. The ion crossover occurs more locally within the ion diffusion region whereas the electron crossover occurs over a wider region as its mechanism does not require electrons to pass through the electron diffusion region. This flow crossover occurs both in symmetric reconnection and in a more complex scenario such as a guide-feld asymmetric reconnection, suggesting that it is a general feature of collisionless magnetic reconnection. Recognizing the existence of the flow crossover can be important in improving our understanding of reconnection in many situations. This research has been partially supported by Thailand's National Science and Technology Development Agency (NSTDA): High-Potential Research Team Grant Program (N42A650868), grant MRG6180176 from Thailand Science Research and Innovation, and by a grant from Kasetsart University Research and Development Institute.

How to cite: Malakit, K., Pianpanit, T., Prapan, P., Ruffolo, D., Pongkitiwanichakul, P., Shay, M., Cassak, P., and Suetrong, P.: Flow Crossover during Collisionless Magnetic Reconnection: A Particle-Labelling Particle-in-Cell Study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9773, https://doi.org/10.5194/egusphere-egu23-9773, 2023.

Turbulence
vEGN.5
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EGU23-10328
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ECS
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Yong Ji, Chao Shen, Lan Ma, Nian Ren, and Nisar Ahmad

Magnetic field gradients determine magnetic topological structure and current density in space plasma turbulence. This study uses multi-point method analyze high-quality field and plasma data measured by the Magnetospheric Multiscale (MMS) mission in the turbulent magnetosheath. The statistical properties of the curvature of the magnetic field line and the geometric invariant of the magnetic field gradient tensor are further investigated. The results show that the probability distribution function of curvature has two scaling laws. There is a correlation between large curvatures and pressure anisotropy, indicating the acceleration due to curvature drifts. During strong magnetic field, flux ropes and tubes are the most possible magnetic structures. Statistics in the plane formed by geometrical invariants show that about 23% are force free structures consist of 20.5% flux tubes and 79.5% flux ropes. The remaining actively evolved structures are comprised of 30% flux tubes and 70% flux ropes. Moreover, the conditional average of current density and Lorentz force decomposition in geometrical invariants plane are conducted. Results show that flux ropes carried more current density than flux tubes for same geometrical invariants, and flux ropes tend to associate with magnetic pressure force and flux tubes tend to associate with magnetic tension.

How to cite: Ji, Y., Shen, C., Ma, L., Ren, N., and Ahmad, N.: Analysis on magnetic field gradients in turbulent magnetosheath by using MMS data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10328, https://doi.org/10.5194/egusphere-egu23-10328, 2023.

vEGN.6
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EGU23-16954
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ECS
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Highlight
Jeffersson Andres Agudelo Rueda, Yi-Hsin Liu, and Kai Germaschewski

Energy dissipation in collisionless plasmas is one of the most outstanding open questions in plasma physics. Magnetic reconnection and turbulence are two phenomena that can produce the right conditions for energy dissipation. These two phenomena are closely related to each other in a wide range of plasmas. Turbulent fluctuations can emerge in critical regions of reconnection events, and magnetic reconnection can occur as a product of the turbulent cascade. Moreover, the presence of a turbulent field can affect the onset and evolution of magnetic reconnection. In this study, we perform 2D and 3D particle-in-cell simulations of a reconnecting Harris current sheet in the presence of turbulent fluctuations to explore the effect of turbulence on the reconnection process in collisionless plasmas. We use the Langevin antenna method to drive turbulence in the reconnecting magnetic field. We compare our results with existing theories.

How to cite: Agudelo Rueda, J. A., Liu, Y.-H., and Germaschewski, K.: On the Effect of Driving Turbulence on Magnetic Reconnection: A Particle-In-Cell Simulation Study, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16954, https://doi.org/10.5194/egusphere-egu23-16954, 2023.